1. Field of the Description
The present invention relates, in general, to devices and methods for providing a three-dimensional (3D) display in a glasses-free manner, and, more particularly, to a 3D display device providing back lighting and optics to present left and right eye images to each viewer's left and right eye, respectively, regardless of the position of the viewer within a viewer space (e.g., regardless of whether the viewer is in the front row or back row of a theater or ride vehicle with tiered seating and whether the viewer moves their head from side-to-side while viewing the 3D movie or display).
2. Relevant Background
Displays that provide the illusion of three dimensions have experienced a rebirth in the past few years. For example, a number of 3D televisions are now available for use in homes and home theaters. These 3D televisions generally operate by displaying a stream of left and right eye images in an alternating or time-multiplexed manner (e.g., left-right-left-right). Switching occurs so quickly that the viewer does not sense a flicker or change in the display. The viewer wears special headgear or glasses that operate in a synchronized manner with the display to only allow the light associated with the left eye image to reach the viewer's left eye and with the right eye image to reach the viewer's right eye.
For example, the 3D glasses may be shutter glasses that rapidly switch between allowing light to reach the left or the right eye, with the shuttering operation controlled to be time-synchronized with the display (e.g., a liquid crystal display (LCD) television monitor or the like). In other cases, the television monitor or display is configured to output two different types of polarized light to present the left and right eye images. In this case, the viewer typically wears glasses with two different lenses that are polarized in a manner to allow the left eye to view light from the display polarized in one manner and the right eye to view light from the display polarized in a second manner. Such polarized 3D glasses have been in use in theaters for many years.
While most commercial displays rely on the use of special glasses, it is generally agreed by those in the 3D entertainment industry that displays able to provide a 3D viewing experience without glasses or headgear offer significant advantages. Presently, there are 3D display systems that can deliver left eye images to a viewer's left eye and right eye images to a viewer's right eye. However, these 3D display systems each have significant limitations. Some 3D display systems require the viewer to have their head in a specific position and to not move at all during the viewing experience as this may cause the wrong image to be viewed (e.g., the right eye to see the left eye image stream or vice versa) or to lose the image altogether. In other implementations, the viewer can move but complex tracking equipment is used to identify an approximate location of the viewer's eyes. The 3D display system then reacts to the new position by changing the output of the display to deliver the left and right eye images to the viewer. Both of these systems are generally limited to use with a relatively small audience, such as 1 to 4 viewers or the like, and these systems may be expensive to design and manufacture, which has resulted in only very limited adoption of such 3D display systems nationwide.
Hence, there remains a need for display technology that can provide 3D stereo images to audiences without the need for the audience members or viewers to wear glasses or special headgear. Preferably, such display technology would be suited for larger audiences of up to 20 to 40 or more members/viewers. Further, it is desirable that the technology be relatively inexpensive to implement (although this may not be a limitation in some settings) so as to allow more widespread use including home theater settings. Additionally, the 3D display technology should be adapted such that the viewers do not have to remain in one position throughout the experience (e.g., can move their head) and can be at various heights and viewing distances (e.g., seated in a theater or ride vehicle with rows of seats that are tiered with each row being further from the screen and higher from a reference plane to allow viewing that is unobstructed by viewers in lower rows).